Unless otherwise indicated herein, the materials described herein are not prior art to the claims in the present application and are not admitted to be prior art by inclusion in this section.
A challenge for optics communications may include coupling a light beam from a fiber (e.g., a single mode fiber (SMF)) into a silicon photonics chip (or other integrated waveguide device) or vice versa. A mode diameter size for a waveguide on the silicon photonics chip may be about a micrometer (μm) or less than 1 μm, while a mode diameter size for an SMF fiber may be about 10 μm, resulting in a mismatch between the waveguide and the SMF fiber. Loss may be incurred if a light beam is coupled directly from the SMF fiber into the waveguide on the silicon photonics chip or vice versa.
A grating coupler may be used to aid in the light beam coupling between the SMF fiber and the waveguide. For example, the grating coupler may include a grating at an end of the waveguide, so that a light beam that propagates through the waveguide may be diffracted out of the waveguide from the grating coupler and may then be coupled into the SMF fiber. In another example, the grating coupler may allow beam spot conversion from a mode diameter size with a range of 300 nanometers (nm) to 500 nm (or another suitable range) in a confined silicon (Si) waveguide to a mode diameter size of about 10 μm (or another suitable value) in a SMF fiber. The grating coupler may also allow on chip testing, which is beneficial to mass production of silicon photonics wafers and other integrated waveguide devices.
However, the grating coupler may have a limited coupling bandwidth. For example, a lens may be placed between the fiber and the grating coupler to focus a light beam from the fiber to the grating coupler. However, the light beam outputted from the lens may have a fixed input direction to the grating coupler. The fixed input direction may lead to an acceptable coupling efficiency for a particular wavelength on the grating coupler, which may pass the light beam to a waveguide on a silicon photonics chip. However, the grating coupler is sensitive to the wavelength of the light beam. If the wavelength of the light beam changes, the fixed input direction of the light beam from the lens to the grating coupler may cause the grating coupler to send the light beam to a wrong direction and therefore the light beam may totally or partially miss the waveguide, resulting in a low coupling efficiency of the grating coupler.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.